1. Field of the Invention
The instant invention relates generally to articles of clothing which have enhanced ultraviolet radiation absorption for protecting the wearer from the deleterious effects of ultraviolet radiation, and more specifically to articles of clothing which have been treated with anthraquinone, melanin or combinations thereof.
Most skin cancers in humans can be categorized as basal cell carcinomas, squamous cell carcinomas or melanomas. Each year in the United States, more than 500,000 people are diagnosed with basal cell carcinomas, 100,000 with squamous cell carcinomas and 30,000 with melanomas. It has been estimated that more than 90% of these skin carcinomas are caused by exposure to ultraviolet (UV) radiation exposure. As a result of ozone depletion in the upper atmosphere, human exposure to UV radiation has been increasing dramatically in recent years, especially in the higher latitudes, where the ozone depletion has been relatively greatest. In Australia, for example, over 100,000 people die each year from skin cancer. Accordingly, it has become more important for people to limit their exposure to UV radiation. This can be accomplished through various means, including the use of sunscreens and UV-resistant articles of clothing.
Sunlight is composed of 66% of infrared light (manifested as heat), 32% visible light, and 2% ultraviolet light (UVL). UVL can be subdivided into ultraviolet A (UVA, wavelength 320-400 nm) and ultraviolet light B (UVB, 290-320 nm). UVB is the main cause of sunburn, with UVA supplementing the effects of UVB on the skin. UVA, having a longer wavelength than UVB, however, can penetrate deeper into the skin. It is believed that UVA like UVB also plays a part in premature skin aging and other skin problems such as skin cancers. With this in mind, it is important for UV-resistant articles of clothing to be resistant to both UVA and UVB radiation.
The degree of protection against UV radiation afforded by clothing is highly variable and depends on a number of factors. One factor is the permeability of the factor. Specifically, a fabric can be made relatively UV-resistant by providing a relatively tight weave or a very high thread count, or by coating the fabric. Both of these approaches greatly reduce or eliminate the apertures in the fabric, thus decreasing UV transmission through the fabric. While this may increase UV protection, it usually produces a material which can be heavy and/or uncomfortable to wear, particularly in hot temperatures when UV radiation is generally highest. Another factor is the UV absorption characteristics of the fabric. The characteristics which are of principal interest are the transmission characteristics of the yarn or fiber, particularly the proportion of UV radiation which is transmitted through or along the fiber or yarn, as opposed to being absorbed or reflected. Accordingly, the present invention concerns the treatment of lightweight, breathable materials with a UVR-absorbing substance to produce a UV-resistant fabric which is also comfortable, particularly in warm weather.
2. Description of the Prior Art
Ultraviolet radiation (UV) resistant fabrics are known in the art. For example, U.S. Pat. No. 5,374,362 (McFarland, S.M., Dec. 20, 1994) discloses a UV-resistant formula for treating vinyl or leather comprising, as the UV-resistance providing compound, 2-(2H-benzotriazole-2-yl)-6-(dodecyl)-4-methylphenol, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole or beta-(3-(2H-benzotriazole-2-yl)-4-hydroxy-5-tert-butylphenyl)propionic acid methyl ester.
U.S. Pat. No. 5,458,956 (Shi, L., et al., Oct. 17, 1995) discloses a UV-resistant tent fabric manufactured from woven polyethylenenaphthalatebibenzoate yarns.